The present invention relates to vertically slidable windows, and more particularly to a jamb liner and friction balance useful in such windows and particularly useful for "cottage-style" windows, i.e., those having "non take-out" sash.
The vertically slidable, "double-hung" window has gained widespread popularity in both residential and commercial constructions. Basically, this window includes a jamb along each side and a pair of the same-sized sash mounted in parallel offset vertical alignment for sliding, by-pass movement between the jambs. Some form of balance or positioner, such as friction shoes or the like, are included in such window assemblies for at least one of the sash so that it can be slid within and stationarily positioned along its travel between the jambs.
One common type of double-hung window is known generally as the "cottage-style" window, which is usually of a comparatively simple and inexpensive type wherein a pair of jamb liners are fixedly secured within the window jamb and the sash is slidably supported between the jamb liners but not tiltable or removable for cleaning, as in more typical but more expensive double-hung windows. In cottage-style windows, each sash usually defines a "plow" (i.e., a continuous groove) along each side, opening toward and interfitting with a protruding ridge or flange on each jamb liner, with the plows and ridges cooperating to maintain the sash or track throughout their travel. The jamb liners also seal, at least to some extent, the sash within the jamb. As indicated above, in double-hung windows the jamb liners incorporate some form of balance and/or friction device to support the sash in various opened (raised) positions, but in cottage-style windows, such refinements are usually absent and whatever frictional contact exists between the jamb liner and sash itself must be relied upon to hold the sash in an elevated position. Since this is unlikely to give good results, the user must typically resort to use of some extraneous object to prop the sash up if he desires to have the window open.
It is much more desirable, in any double-hung window, including cottage-style windows, to provide friction shoes as positioners or "balances", which in double-hung windows typically ride within channels defined by the jamb liner, to hold the sash in place once it is raised. In such double-hung windows where friction shoes are provided, the jamb liner is typically fabricated of a relatively flexible polymeric material such as PVC and typically comprises a base portion extending the full height of the jamb and a pair of spaced sidewalls extending generally perpendicularly from the base portion to define a generally rectangular channel. A pair of abutment walls extend inwardly toward one another perpendicularly from the opposite sidewalls, and the friction shoe rides within the channel, frictionally engaging both the base portion and the abutment walls. A portion of the friction shoe extends between the two abutment walls to support the sash within the jamb liner.
Such friction shoes are usually considered to be useful only with sash having rectangular channels, however, whose spaced sidewalls (or rear and front walls) provide opposite supports for the abutment walls of the rectangular jamb channel, which otherwise flex (distort) outward under the pressure exerted by the friction shoe. Nonrectangular channels (or plows) may not adequately support the relatively flexible vinyl abutment walls, and consequently the unsupported abutment walls may flex excessively under the pressure of the friction shoe so that the sash is not properly supported. Therefore, the friction shoe concept has not previously been used with window sash whose side channels, or plows, have other than rectangular cross sections.